The present invention relates to a storage controller and a method of controlling the storage controller.
The storage controller is constructed such that the storage devices such as hard disk drives and the like are disposed therein in the form of an array, and provides a host computer (sometimes referred to as “host” hereinafter) with a storage region based on, for example, RAID (Redundant Array of Independent Disks). At least one logical volume (logical storage device) is formed on a physical storage region (physical storage device) which is provided by a group of storage devices, and the host is provided with this logical volume. The host reads and writes data with respect to the logical volume by transmitting a predetermined command.
Due to various regulations, the business organizations and the like need to save various data such as e-mail data, contract data, sales data, and customer data for a certain period of time. When the data is required for an audit, the saved data have to be accessed immediately.
Tape devices are used relatively widely in order to save a large amount of data. However, when using the tape device, a magnetic tape stored with desired data needs to be carried away from a storehouse and set in a reader, thus it is not possible to promptly access the saved data.
Recently, SATA (Serial AT Attachment) disks comprising SATA interfaces started to become prevalent as relatively inexpensive hard disk drives. Therefore, storage controllers that use the SATA disks instead of the tape devices as the device for saving data are coming in.
However, the SATA disks are not as reliable as the FC (Fiber Channel) disks with the FC interfaces, thus there is room for improvement in the SATA disks in terms of the availability of the storage controller. Therefore, there is proposed a technology of individually performing ON-OFF control on the powers of the hard disk drives that are installed in the storage controller (U.S. Patent Application Laid-Open No. 2004-0054939).
In the technology described in the abovementioned patent literature, the power of the disk drive is switched ON when the disk drive is used, and the power is switched OFF when the disk drive is not used, whereby the energization time in the hard disk drive can be reduced to improve the reliability of the storage controller.
However, the host does not access the data while being aware of each of the disk drives, but accesses the data by considering the logical volume as the target of access. Further, a plurality of types of logical volumes with different characteristics are sometimes set in the same group of disk drives. Therefore, simply switching the powers ON and OFF the disk drives individually is unlikely to reduce the energization time in each of the hard disk drives.
For example, when the logical volume which stores frequently-accessed data, and the logical volume which stores infrequently-accessed data use the same group of disk drives, there is less opportunity to turn off the powers of the group of disk drives. The conventional technologies do not sufficiently consider the characteristics or arrangement of the data stored in the disk drives, thus it is difficult to reduce the energization time (operating time) in the disk drives.